Scientists have placed several specimens in the order (called Mantophasmatodea) - one of which had been held in a European museum after spending 16 years awaiting classification.

Another was found trapped in a 45-million-year-old chunk of Baltic amber.

The insects, which are about two centimetres long, look like a cross between a stick insect and a preying mantis.

The bugs are thought to eat other insects since the stomach contents in some of the specimens studied to date included leg parts.

Living fossil

Scientists have so far named two species (Mantophasmatodea zephyra and Mantophasmatodea subsolana) in the new order, and put a third insect, the Baltic specimen, in its own genus (Raptophasma), a slightly more general grouping.

DNA analysis will help place the order in the overall insect family tree

The new order is based on the way the insects look - they have a distinct arrangement of internal and external body parts. DNA analysis will help scientists work out how the Mantophasmatodea order fits in with the rest of the insect family tree.

Living populations of the insects were found in western Namibia on the Brandberg Mountain during an expedition funded by Conservation International.

Scientists from the Washington-based organisation say the new insect order may have lived in Brandberg's unique habitat for millions of years with no interaction with other species.

Brandberg is a 120-million-year-old massif, isolated from other mountains by hundreds of kilometres of barren sand, and is well known for its animal species that have been found nowhere else on Earth.

Living fossil

The researchers say the insects are like "living fossils" - the last witnesses of a time when Africa and America were part of the same landmass.

Entomologist Piotr Naskrecki said: "This discovery is comparable to finding a living mastodon or sabre-tooth tiger.

"It tells us that there are places on Earth that act as protective pockets, preserving tiny glimpses of what life was like millions of years ago."

The discovery of the new insect order was formally announced in the journal Science. It brings to 31 the total number of insect orders.

"This is the first time since 1914 that a newly described extant insect taxon has proved unplaceable within a recognised order," said team leader Klaus-Dieter Klass, of the University of Copenhagen's Zoological Museum.